1. Technical Field
The present invention relates to a flat bottom pillow pouch constructed using a modified vertical form fill and seal packaging machine, and the method for making the same that provides for a single-piece construction of a bag suitable for retail snack food distribution.
2. Description of Related Art
Many snack foods, like chips, pretzels, etc. are packaged in pouches formed of a very thin packaging film. These packages can be manufactured on vertical form, fill, and seal packaging machines that, as the name implies, forms a package, fills it with product, and seals the filled package. An example of a vertical form, fill, and seal machine for making pillow-pouch packages is exemplified in FIG. 1 of U.S. Pat. No. 6,718,739. Such packaging machines take packaging film from a sheet roll and form the film into a vertical tube around a product delivery cylinder. The vertical tube is vertically-sealed along its length to form a back-seal. The machine applies a pair of heat-sealing jaws against the tube to form a transverse seal. This transverse seal acts as the top-seal on the bag below and the bottom-seal on the package being filled and formed above. The product to be packaged, such as potato chips, is dropped through the product delivery cylinder and formed tube and is held within the tube above the bottom transverse seal. After the package has been filled, the film tube is pushed downward to draw out another package length. A transverse seal is formed above the product, thereby making a bag and sealing the product within the bag while simultaneously forming a film tube above the product. The package below said transverse-seal is separated from the rest of the film tube by cutting across the sealed area. An example of the resultant standard pillow pouch bag is depicted by FIG. 3a of U.S. Pat. No. 6,722,106.
The packaging film used in such process is typically a composite polymer material produced by a film converter. For example, one prior art composite film used for packaging potato chips and like products in a standard pillow pouch bag uses a sealable inside, or product side, layer which typically comprises metalized oriented polypropylene (“OPP”) or metalized polyethylene terephthalate (“PET”). A sealant layer disposed upon the product side of the metalized film enables a hermetic seal to be formed by the transverse sealing jaws at a temperature lower than the melt temperature of the film. Typical prior art sealant layers include an ethylene-propylene co-polymer and an ethylene-propylene-butene-1 ter-polymer. The metalized film layer, which is usually metalized with a thin layer of aluminum, provides excellent barrier properties.
Barrier properties in one or more layers are important in order to protect the product inside the package from light, oxygen or moisture. Such a need exists, for example, for the protection of foodstuffs, which may run the risk of flavor loss, staling, or spoilage if insufficient barrier properties are present to prevent transmission of such things as light, oxygen, or moisture into the package.
Adjacent to the metalized inside layer is a laminate layer, typically a polyethylene extrusion, and an outer ink or graphics layer. The ink layer is typically used for the presentation of graphics that can be viewed through a transparent outside layer, which layer is typically OPP or PET. The overall film thickness of this prior art film composition is typically less than 225 gauge. Such prior art film composition is well known in the art and disclosed in the discussion related to FIG. 1 in U.S. Pat. No. 7,189,300, which is hereby incorporated by reference.
The prior art film composition discussed above is ideally suited for use on vertical form and fill machines for the packaging of food products. The use of OPP or PET for the outside layer and the inside layer further makes it possible to heat seal any surface of the film to any other surface in forming either the transverse seals or back seal of a package.
Ideally, every seal on every package would be hermetic, or leak-proof, even under pressure changes. Without a hermetic seal, any barrier properties provided by the film are ineffective against oxygen, moisture, or aroma transmission between the product in the package and the outside. Hermetic seals are especially important with snack foods, so that flavor and freshness are preserved. Areas where the package has a back seal, folds, or gussets provide extra layers of material in the seal, but this problem becomes more acute with thicker packaging materials, additional folds in the package design, and smaller packages.
One problem with pillow-pouch packages is that they have a narrow, single-edge base made from the bottom transverse seal and therefore such prior art packages are not stable and are unable to stand independently (e.g., without leaning on something) on the bottom transverse seal. It would be desirable to have a pillow-pouch package capable of independently standing on its bottom-transverse seal.
FIGS. 1a-1d depict a vertical, stand-up pouch 100 having a front 102 defined by a top-transverse seal 120 and a bottom-transverse seal 130. Also depicted is a side 110 with a sealed gusset 112 adjacent to the bottom transverse seal 130 and an open gusset 114 adjacent the top transverse seal 120. A gusset is created on the side 110 of a package when four layers of film are captured because of film being pushed or folded inward and sealed together by the transverse sealing jaws when the transverse seal is made. It is not necessary that the transverse seals actually seal all four layers of packaging film together to form a gusset, as demonstrated by the open gusset 114. However, sealing all four layers together can result in a closed gusset 112.
Referring to FIGS. 1c and 1d, four layers of film are also sealed together in the vicinity of the middle of the rear face 106 of the package in the areas indicated by 127 137 if a fin seal is used as the back seal 140. Because such overlapping film is not on the side of the package and is not a result of being pushed inward or folded inward, such areas are not considered a gusset for purposes of this application.
As used herein, a “gusset” is defined as a gusset on the side 110 of a package and includes both open gussets 114 and closed gussets 112.
As shown, the front of the package 102 and the rear-package face 106 are bounded on the sides by heat-sealed creases 104 that run from the top transverse seal 120 to the bottom transverse seal 130. The package depicted in FIGS. 1a-1d is similar to the package disclosed in U.S. Pat. No. 5,398,486. The package depicted in FIGS. 1a-1d is constructed in a method similar to that described above with regard to prior art pillow-pouches. However, to form the side gussets 110 on either side of the bag, the vertical, form, fill and seal machine must be substantially modified by the addition of two moveable devices on opposite sides of the sealing carriage that move in and out to make contact with the packaging film to form the tuck that becomes the side 110 shown in FIGS. 1a-1d. Further, instead of using a single back-sealer to make a back seal 140, the package made in FIGS. 1a-1d require an additional heat sealing device for each crease 104 that is made in the package to provide additional stability to the package. Consequently, a total of five vertical sealing devices are used. Methods for making such vertical creases 104 are described and taught in U.S. Pat. Nos. 5,862,652 and 3,785,112.
As discussed above, it is important that the transverse seals on every package made from this film be a hermetic or leak-proof, transverse seal. This is especially important with low moisture shelf-stable foods and/or other products that are susceptible to oxygen and/or moisture.
FIG. 1d is a top perspective rear view of the prior art package depicted in FIG. 1a and illustrates the relative position and portion of the problem areas 125 126 127 of the transverse seal 120. FIG. 1e is an exaggerated top cross-sectional view of the problem area 125 of the package depicted in FIG. 1d. Referring to FIGS. 1d and 1e, regions 121 and 123 of the top transverse seal 120 each have four film layers that must be sealed together while region 122 has only two layers except at the intersection of the back seal. Similarly, if a lap seal is used to make the back seal 140 the area 127 will have three layers of packaging film and if a fin seal is used, the area 127 will have four layers of packaging film. Because of the change in the number of layers of packaging film, triangularly-shaped capillary leaks, pin-hole leaks, or void spaces 150 (as depicted by FIG. 1e) can occur in packages when side gussets 110 are made in the packaging film. Similar void spaces occur in each problem area as shown by numerals 125 126 127. FIG. 1c depicts locations where these problem areas 135 136 137 can occur on the bottom, transverse seal 130. The problem areas can occur in packages having an open gusset 114 as shown by the top portion of the package in FIG. 1d or in packages having a closed gusset 112 as shown the problem areas 135 136 137 illustrated by the bottom portion of the package in FIG. 1c. 
The prior art solutions to overcoming pinhole leaks requires the film from prior art pillow packages to be modified in some manner. For example, while the top and bottom transverse seals 120 130 have the potential of having a problem areas 127 137, as depicted by FIGS. 1c and 1d, such problem areas can be addressed by use of the film disclosed in U.S. Patent Application Publication No. 2007/0128386, assigned to the same Assignee as the present invention.
Unfortunately, such prior art solution still requires film modification may not adequately address the problem areas 125 126 135 136 that can facilitate oxygen and moisture penetration into a package via the capillary void space 150 as depicted in FIG. 1e. 
Another prior art solution for overcoming pinhole leaks is to add two or three times more sealant to the product facing layer, such as the product facing OPP layer. Another solution to overcoming such shortcoming is to use an additional film layer to try to fill up the capillary void space. The additional film layer is typically a 1 to 2.5 mil (100 to 250 gauge) linear low density polyethylene that must be laminated to the inner metalized OPP layer. Consequently, such films typically require a tandem lamination to make the requisite multi-layer film and substantially more film material must be used than is required for a standard pillow pouch package. The thickness of a film typically used for packages having gussets is usually greater than 300 gauge, which is at least about 33% more film than used in standard pillow pouch packages.
For example, U.S. Pat. No. 7,122,234 teaches that laminates used to make such packages require sufficient bending stiffness to be suitable for continuous high speed packaging. The '234 Patent teaches that sufficient stiffness occurs when the laminate thickness exceeds 110 micrometers or 433 gauge units (1 micron or micrometer=3.937 gauge; 100 gauge=1 mil=0.001 inches). European Patent Application 1 283 179 discloses a microwave heatable food product package associated with the trade name TETRAWEDGE. When measured, the TETRAWEDGE package revealed a thickness of 12.5 mil or 1250 gauge. One apparent consequence of using such thick material is that a crease pattern is applied to the packaging material prior to package formation to permit the material to be folded along inclined lateral corners and along base corners. Similarly, U.S. Pat. No. 5,508,075 discloses the need for crease lines to be stamped or otherwise impressed into the surface of the packaging material. It would be desirable to make a flat bottom pillow pouch using the same film as is used with prior art pillow packages without compromising the hermetic sealing properties of the transverse seal.
In one aspect, the package should be made to avoid open or closed gussets and to minimize the problem areas at an upper or lower transverse seal that occurs because of a change in the number of layers and regions of transition that can create capillary void spaces 150 in the transverse seals. In one aspect, the package should have three or more distinct edges defining the package bottom to permit the package to stand upright on the bottom transverse seal. In one aspect, the package should be made of the same film material and utilize the same film thickness used to make standard pillow pouch packages. In one aspect, the package is made with a film material without the need for crease lines to be stamped or otherwise impressed into the package film.